This invention relates to rolling doors and in particular an operating mechanism for opening and closing a rolling door.
The use of rolling doors, particularly for industrial applications and for mining, is well known. These doors can be of various constructions including flexible doors made from rubber or plastic sheets. The door is rolled up about a horizontal shaft extending across the top of the door opening. There can be a spring loaded barrel arranged on the shaft about which the door is rolled. The purpose of this barrel is to overcome the gravitational forces acting on the door so that the door will open with relative ease. It is common to provide an electric operator including an electric motor to open and close the door. Vertical guideways are generally provided along the sides of the doorway to accommodate the edges of the flexible door.
U.S Pat. No. 4,690,195, D. B. Taylor, issued Sept. 1, 1987, teaches operating mechanisms for a rolling door having a power operated means for roll up of the roll door to open the door opening and a power operated means for rolling down the door to close the door opening.
In one embodiment taught in the aforementioned U.S. Patent the drive gear for the door shaft which supports the roll door and the drive gear for the idler shaft are floatingly mounted on such shafts for free rotation; a dog member is mounted for rotation with each of the door and idler shafts and a dog engaging pin is mounted on each of the drive gears. The pin and dog member associated with the drive shaft and idler shaft, respectively, interact for positive rotary drive of the drive shaft or idler shaft, as required. This arrangement accommodates excess winding and unwinding forces which develop at the idler gear as a result of variation in the actual linear velocity of travel of the unwound end portion of the roll door during winding and unwinding; the variation in linear velocity arises from the variation in the diameter of the windings of the rolled door on the door shaft as it is rotated, and the constant speed of rotation of the drive and idler shafts.
The aforementioned arrangement requires precise relative location of the dog member and pin associated with each shaft to ensure that engagement and positive drive only occurs at appropriate configurations relative to the wound end position of the roll door.
It is an object of the present invention to provide a simpler arrangement and structure of operating mechanism.